(!) That was good, because:
1. blocks the dangerous white e-pawn;
2. leaves white bishop at h1 almost out of the game;
3. stops several mating lines;
4. takes 4 pawns in a single move (this will reveal decisive);
note that the rook in c1 could also be taken, but the g1 Bishop would
remain very effective against black pawns.
(!) Now the King is protecting the 4 most important pieces (d and e pawns,
rook and knight) against white Knight sequences. Trying to defend black
e1 Knight would lead to complications, as also trying to promote black g7 pawn.
9.Nc3 Nd5 N:c7 Ne6 N:g7 Ne7 Ng6 K:e1 N:h8+
That is it.White had to finish with a check, but the game is lost now.
Several other sequences loose too.